THE SPIDER–HUNTERS
WHILE Ammophila provides caterpillars for her larva, and Bembex, after
the manner of the social wasps, feeds her young from day to day on
dead flies, the Pompilidæ, so far as their habits are known, all prey
upon spiders. The family is a large one in the United States, one
hundred and twenty–seven species having been described. The members of
the group differ in size, color, and habits, and the individuals of
the same species show the very considerable amount of variation which
seems common to all those groups of animals which have been carefully
studied. Happily the old notion that habits and instincts, unlike
structural peculiarities, are always uniform, is no longer insisted
upon, and there is ample evidence for the opinion that functional
variations are as common as morphological. We have studied five species
of this family, and have found their respective rôles of great interest.
According to Fabre, the French members of this genus, although they do
not make their own nests, still exercise some foresight in the matter
by selecting a suitable crevice before catching their prey. Among the
species that we have studied, quinquenotatus, biguttatus, fuscipennis,
marginatus, and interruptus first catch the spider and then make the
nest; while calipterus and scelestus prepare the nest before capturing
their prey.
[Illustration: TORNADO WASP (POMPILUS QUINQUENOTATUS) DIGGING NEST]
Quinquenotatus is usually rather less than half an inch in length and
is black, the abdomen having a variable number of white bands and a
white tip.
It was on the last day of July that, as we were walking through the
bean field, we saw a cloud of fine dust which came spurting up out of
the ground like water in a fountain. By watching intently we saw that
the cause of the commotion was the rapid action of the legs of some
little creature that was almost hidden in the earth, and this proved to
be our first example of P. quinquenotatus.
She was working away as furiously as though she had studied the poets
and knew her _carpe diem_ by heart. Faster and faster went the slender
little legs; higher and higher rose the jet of dust above her. Then
suddenly there was a pause. The burrower had met with some obstacle. A
moment more and she came backing out of the hole, her feet slipping on
its crumbling edges. In her mandibles she carried a pebble, which was
taken to a distance of four or five inches. Then, moving quickly, she
swept away the dust that had accumulated near the mouth of the nest,
reëntered the hole, and resumed the labor of excavation.
We thought that the rate at which she worked was too violent to be kept
up very long; and sure enough, before ten minutes had passed the nest
was deep enough for her purposes, and we afterward learned, to our
chagrin, that it was too deep for ours. The wasp came out, circled
round the spot three or four times, and then flew off like a hurricane.
Never have we seen a creature so fiery, tempestuous, cyclonic. Before
we knew her proper title we took to calling her the tornado wasp, and
by that name we shall always think of her.
[Illustration: POMPILUS QUINQUENOTATUS]
Her flight was too rapid to follow, but in a minute we saw her
returning. She was carrying a spider, a good–sized specimen of Epeira
strix, which she had evidently deposited somewhere in the neighborhood
before beginning to dig. Alighting near by, she left the spider lying
on the ground, while she ran to her nest and kicked out a little more
earth. Then seizing it by one leg, she dragged it, going backward
herself, into the nest. She remained hidden for about two minutes, then
reappeared, and, seeming to be in as great a hurry as ever, filled the
hole with dirt. To disguise the spot and render it indistinguishable
from the rest of the field was her next care. Hither and thither she
rushed, now bringing little pellets of earth and placing them above
the nest, now sweeping away the loose dust which might suggest the
presence of the _cache_, and now tugging frantically at a stone which
she wanted to place over the hidden treasure, but which was too deeply
embedded in the earth to yield to her efforts. She did her work
faithfully, although with such eager haste that all was completed at
the end of twenty minutes from the time we saw her first. So well was
the place hidden that it was only by careful orientation that we could
be certain of its exact locality.
Her task accomplished, away flew our little tornado as though she
were pursued by the avenging spirits of all the spiders that she had
murdered, although more probably she was off in quest of another of
those meek and helpless victims.
“Now,” we said, “we will trace out the nest and make a drawing of it.
We will take the spider home and note its condition from day to day,
watching at the same time the development of the larva.”
Enjoying this little air–castle, we began to excavate. Having had
experience with the nests of Ammophila and Diodontus, and knowing that
the task might not be so easy as it looked, we went to work with all
possible care. It seemed, however, that some magician’s trick—some
deception of the senses—had been played upon us. We saw the spider
interred; we at once dug up the place and found nothing. Slowly and
carefully we enlarged our circle. We went down deeper until the opening
was large enough to hold a thousand spiders,—still nothing. Then we
tried another plan. Gathering all the earth that we had taken out, we
sifted it through our hands—in vain. At last we acknowledged ourselves
beaten, and trudged home empty–handed.
Our pride was destined to be still further humbled. Three times within
that same week we saw the tornado wasp bury her spider, and three
times we failed, just as incredibly, to find it. On the last of these
occasions we did not let her fill the nest, attempting to follow the
tunnel and get out the spider as soon as the egg was laid, but the
loose, unstable character of the soil defeated us.
Our fifth example, however, dug her nest, not among the beans but lower
down in the potato field, where the ground was firmer; and here we made
our first successful excavation,—successful only up to a certain point,
since in getting out the spider we dislodged the egg, and although it
was at once replaced it never developed. The spider was placed three
inches below the surface, but we could not trace the tunnel. At our
next opportunity, wishing to make good this failure, we placed a blade
of grass in the opening just after the wasp began to fill it. On being
disturbed she assumed the most comically threatening aspect, whirling
around, lifting her wings, and then circling about us. As soon as we
moved back she dashed at the grass–blade and pulled it out with great
energy. A few minutes later we made a similar attempt, and again she
frustrated our plan; but when we inserted the grass–blade for the third
time, the nest being now half filled, she let it remain. Some hours
later, with this to guide us, we succeeded in tracing the nest, but
much to our disappointment found it transformed into a banqueting hall.
Scores of tiny red ants had discovered this rich store of food. They
had eaten the egg and were rapidly finishing the spider.
Twice afterward, in opening these nests, we found the same ants in
possession before us. It is probable that they are a formidable enemy
to this and other species of Pompilus; but they seem to find the spider
by burrowing beneath the surface, so that the elaborate hiding of the
nest from above cannot be meant as a protection from them.
[Illustration: EXAMPLE OF EPEIRA STRIX THAT HAS BEEN PARALYZED AND HUNG
UP ON BEAN PLANT BY POMPILUS QUINQUENOTATUS, THAT IT MAY BE OUT OF THE
WAY OF ANTS WHILE SHE DIGS HER NEST]
Pompilus quinquenotatus has a decided preference as to the spider that
she takes. While Pelopæus and Trypoxylon are entirely indifferent
both as to size and species, and the more nearly related Pompilus
marginatus takes Thomisus, Drassus, Attus, Agalena or Lycosa, this more
fastidious wasp will not be tempted from the spider of her choice.
In more than fifty examples the victim in the play was invariably
Epeira strix. If she must confine herself to one species she has made
a fortunate selection, since there is no other spider so common in
our neighborhood, not only in the woods, but around the barns and
outbuildings. Most frequently it was the female that was taken, but
this does not imply a preference for that sex, since the females are
more abundant than the males. We have never seen the spider captured
and do not know where the sting is given, but certainly this wasp
wounds her prey very severely. The spiders that we took from her were
either dead, or so completely paralyzed that it required great care and
the use of a magnifying glass to determine that they were alive.
The next stage of her proceedings we are familiar with, as we have
frequently seen the wasp carry the spider. Unlike her sister,
marginatus, she usually flies with it, and seems not at all encumbered
by its weight. In many cases, however, she drags it, holding it by one
leg and running rapidly backward.
A suitable place for the nest being found, the spider is very prettily
taken care of while the work is in progress. A plant, usually a bean or
a sorrel, is chosen, and the strix is hung in the crotch of a branching
stem, where it will be safe from the depredations of ants. This
precaution is not always taken. We have many times seen the spider left
on the ground, although there were plenty of plants at hand.
The next point is to decide upon the precise spot for the nest,
and here our wasp shows herself very uncertain and hard to please.
Never have we seen one settle down and complete her work in the spot
first chosen. She dashes at a place and scratches and digs away with
furious energy for a few minutes, and then, starting up, she darts
wildly hither and thither until a new place, near by, is fixed upon
and another beginning made. In one instance eight nests were started
and some of them nearly finished, the little worker seeming to be
beside herself with excitement. After the decision is finally made the
tunneling is a rapid process. In one case it took the wasp a whole hour
to complete the work, but out of the thirty nests that we saw made,
nineteen were finished in from twenty to twenty–five minutes. Like
Fabre’s Sphex the wasp interrupts herself three or four times to visit
her spider and make sure that it is safe. When all is done she brings
the strix to within a foot or two of the opening, runs to the nest to
take a final look, and then, going backward herself, pulls it inside.
In two instances we saw the fidgety little creature go through a most
comical performance, which again recalls the Sphex of Fabre. Leaving
her treasure on the ground, she ran to the nest and kicked out a little
more earth; hastening back she dragged it an inch nearer; then away she
went to the nest again for more digging, and so on, dropping her spider
half a dozen times before she at last brought it home. In two other
cases in which there was no such anxiety about the size of the nest,
there was, in reality, more reason for it. Indeed, in one instance the
opening had to be enlarged before the spider could be taken in. There
is a wide–winged parasitic fly that, having nothing else to do, lays
prodigious numbers of eggs, not in any particular nest, but at the
edge of holes wherever it may chance to see them. It hovers about over
the ground until it comes to an opening, dips down twice or thrice,
ovipositing each time, and then passes along. The habit of scratching
out a little dirt at the threshold, just before the prey is brought in,
seemingly from a desire to enlarge the nest, or in other cases from
mere nervousness, is perhaps of use in destroying these eggs, which
might otherwise adhere to the spider or caterpillar as it is dragged
over them.
The laying of the egg takes only two or three minutes, and then the
hole is filled up. In this part of her work quinquenotatus shows a
great deal of variation, sometimes coming out of the hole and sweeping
in the dirt with her first legs and sometimes standing in the tunnel
while she draws the earth in with her mandibles and then jams it down
with the end of her abdomen. The former plan was in vogue in the
garden, while the latter was more common with the wasps on the island.
After the hole is filled the spot is covered with pellets of earth
and pebbles brought from a little distance, very much as is done by
Ammophila.
When we found that quinquenotatus was a very common species, and that
nearly every day brought us a fresh example, we thought that we had
the question of its stinging habits in our own hands. What could be
easier than to carry a strix about with us and to exchange it, when
opportunity offered, for the paralyzed spider of the wasp? The good
results obtained by Fabre and Marchal from this manœuvre made us
confident of success. We did not doubt that when the wasp came for her
spider and found it livelier than it ought to be, she would repeat the
stinging operation before our eyes.
Accordingly, the next time that we saw quinquenotatus digging we made a
diligent search for her spider, and soon found it on a bean plant five
feet away. Just as we discovered it, however, the wasp swooped down and
carried it to some purslain, close to the hole, where she hung it up
again, while she went to make her final preparations at the nest. We
seized our chance, and quickly substituted a fresh strix for the one
that had been paralyzed. According to the habit of its species when
danger threatens, it kept perfectly quiet, and when the wasp returned
it was hanging there as motionless as a piece of dead matter. How she
knew the difference was a mystery, but she would not touch it. She
seemed to think that she had made a mistake in the locality and that
her own spider must be hanging somewhere close by, for she hunted all
over that plant and then over several others near to it, returning
continually to look again in the right spot. After five minutes she
gave it up, circled about three or four times, and flew off in the
direction of the woods to catch another spider.
Why did she go to the woods? When she realized that the strix she had
stung was gone and that she must have another, why did she not take
the one that hung there in plain view? Our failure could not have been
due to the fact that we had handled the spider, since, when on other
occasions we took one that had been paralyzed, examined it and then
returned it to the wasp, she accepted it without hesitation.
Disappointed though we were at the irrational conduct of our wasp, we
resolved to await her return and to try again. In forty minutes she
came back with another spider, but instead of taking it into the nest
she hung it upon a bean plant near by and then proceeded to dig a new
hole a few inches distant from the first. Foolish little wasp, what
a waste of labor! Truly, if you are endowed with energy beyond your
fellows you are but meagrely furnished with reason.
Again we availed ourselves of our opportunity, and substituted our
spider for hers. This time it had grown weary of playing its motionless
rôle, and frequent readjustments were necessary in order to keep it in
position. At the moment that the wasp came back to take it, the spider
scrambled from its place and began to make its way along the stem. The
wasp evidently saw it, for she hovered over it a moment. She then flew
to the next plant, where she hunted about over the leaves and branches
in search of her lost treasure. After a time she returned. The spider
had now come to a standstill, and the wasp examined it attentively,
although without touching it. She then flew away without circling at
all, which might, perhaps, be taken as an indication that she had no
intention of returning to a place where she had fared so badly.
Just at this moment we chanced to see another paralyzed strix hanging
near by. Again the exchange of our specimen was accomplished; but
when the second wasp came to find her spider she gave us no more
satisfaction than the first. The substitute hung there quietly enough.
We ourselves could not have distinguished it from the original, but
quinquenotatus took a good look at it, decided that something was
wrong, hunted about a little for her own spider, and then flew away.
We had then, as the fruit of our morning’s work, gained nothing in
regard to a knowledge of the stinging habits of our wasp, but at
least we had secured three freshly paralyzed spiders to add to our
laboratory collection. As to the strix that had so kindly assisted us
in our experiments, we placed it on a bush in the pleasantest and most
secluded corner of the garden and left it there, wishing it a long and
happy life.
Later on in the season we tried the same experiment. Taking her spider
from quinquenotatus as she was dragging it to her nest, we offered her
a very lively strix in its place. She would not notice it at all, and
soon flew away. Half an hour later she reappeared, and seemed to be
looking for a place to dig. As she ran about on the ground we offered
her another spider, dropping it on the ground in front of her. This one
behaved admirably, drawing up its legs and keeping perfectly still, not
moving even when she felt of it and turned it over, but it was left
without any display of interest or emotion.
One day we saw a quinquenotatus finish her nest and go after her
spider. She was absent for some time, and when an ant passed by,
dragging a paralyzed strix that had evidently been stolen from some
wasp, we thought that the one we were watching had been robbed, and
rescuing the spider, placed it in the doorway of the nest. We had
judged wrongly, for a moment later our wasp came back bringing her
own spider, and dropping it near by, ran to look at her nest. She was
disturbed at finding the way blocked, and dug out a little earth to
one side of the strix. Then she flew to some holes in the ground not
far away and dug a little, first in one and then in the other. After
this she took a look at her spider, and then went back and dug a little
more at her own nest. Finally she seized the impeding strix by a leg,
dragged it out of the way and paid no further attention to it, storing
her own spider and departing, although the one she had rejected might
have saved a hunting expedition.
At another time we saw two wasps digging their nests two or three feet
apart. One of them finished before the other, and being unable to find
her own spider (probably it had been carried away by the ants), she
seized that of her neighbor and bore it away. The rightful owner saw
from a distance what was happening, and ran to the rescue. A violent
scrimmage ensued, the two wasps clinching and rolling over and over
together. The robber escaped and made off, but was followed and caught
again. She fought so well for her ill–gotten treasure, however, that
she finally conquered the other and hurried off with her prize. She
showed by her manner that she felt the need of haste, for instead of
laying the spider down and looking at the nest, she dragged it directly
in, as though she feared another attack. This was the first time that
we had ever seen these wasps fighting over their prey, and we were
surprised to find that they would take spiders which they had not
captured themselves, since when we had tried to exchange with them they
had refused to carry out our scheme. This was clearly an intelligent
act, and could not be an affair of instinct.
Once again we witnessed a similar struggle. One of these wasps was
laboriously dragging her strix up a steep hillside, when a much bigger
one of the same species descended upon her and seized the spider. She
was loath to give it up, and they both pulled until it seemed as though
the poor creature would be dismembered. The highway robber came off
victorious, and after flying to a distance hung the spider up while she
finished a partly made nest, and then stored it away. It may be said in
extenuation of her conduct that since she had a nest started she had
probably been robbed herself, and therefore felt that she was entitled
to a spider.
The nests of quinquenotatus vary considerably according to the kind
of soil in which they are made, the firm clay of the garden giving a
result quite different from the fine dry earth of the island, in which
they are usually much larger, and scarcely to be distinguished from
the holes of Bembex spinolæ. In both localities, however, the nest
consisted of a short tunnel, running obliquely downward, with a slight
enlargement at the end, but with no change in the direction of the
gallery.
[Illustration: NEST OF P. QUINQUENOTATUS]
In the loose sand of a steep hillside we found that the wasps had a
different method. Their tunnels in this place filled up nearly as
fast as they could dig them, and when they had reached a depth of
half an inch they turned off at a right angle, and excavated in an
entirely new direction. They probably derived some advantage from this
variation, for we saw four in succession follow the same plan, which
certainly appeared to be an intelligent adaptation of means to ends.
We once saw a wasp of this species digging her nest on the Bembex
field. When finished it was a large hole which could not have been
distinguished from those of spinolæ, which were open all about, the
weather being bright and sunny. She flew off, and soon reappeared
with her spider, which was dropped three feet away while she ran to
make sure that all was right; and now followed something that we had
never seen before—she could not find her nest. She flew, she ran,
she scurried here and there, but she had utterly lost track of it.
She approached it several times, but there are no landmarks on the
Bembex field. We have often wondered how they find their own places.
After five minutes our wasp flew back to look at her spider, and then
returned to her search. She now began to run into the Bembex holes,
but soon came out again, even when not chased out by the proprietor.
Suddenly it seemed to strike her that this was going to be a prolonged
affair, and that her treasure was exposed to danger; and hurrying back
she dragged it into the grass at the edge of the field, where it was
hidden. Again she resumed the hunt, flying wildly now all over the
field, running into wrong holes and even kicking out earth as though
she thought of appropriating them, but soon passing on. Once more she
became anxious about the spider, and carrying it up on to a plant
suspended it there. Now she seemed determined to take possession of
every hole that she went into, digging quite persistently in each, but
then giving it up. On one that seemed to be unoccupied she labored at
enlarging the entrance, until we thought that she had mistaken it for
her own, or at least had determined to use it. At last, however, she
made up her mind that all further search was hopeless and that she must
start afresh; and forty minutes from the time that we saw her first she
began a new nest close to the spider, as though she would run no more
risks. This nest was successfully completed, and the spider was stored
away without further misadventure.
The egg of quinquenotatus can be but lightly attached to the spider,
for only once, out of many attempts, did we succeed in getting it
out without displacing it. In this case three days elapsed before it
hatched. The larva ate for a day or two, but then pined away and died.
Another nest was opened on the tenth day after the egg was laid, and
in this the spider had been entirely eaten and the larva was just
spinning its cocoon; so that the larval stage probably occupies about a
week.
A summary of our notes shows a very wide variation in the condition of
the spiders stored by this wasp. Out of eleven that were stung three
were killed at once, two lived four days, one five, one eleven, one
twenty–three, one twenty–five, one thirty–one, and one at least forty
days and probably longer.
We look back with much pleasure upon our acquaintance with this gay,
excitable little wasp. She was so full of breezy energy that it was
always delightful to meet her, and she showed so wide a variation
in individual character that we seldom watched her without learning
something new.
Pompilus fuscipennis, a little smaller than P. quinquenotatus, is
black, with the red girdle that appears so frequently among the
solitary wasps. The first time that we ever saw this wasp she was
running rapidly backward over the bare ground, the brilliant red of her
body flashing in the sunlight as she dragged along a little spider of
the genus Thomisus. Presently she carried it up on to a leaf and began
to bite at it, but being disturbed by an ant, hurried on with a much
agitated manner. Soon she stopped again and resumed her attack, biting
savagely at the legs near their junction with the body, and now,
looking closely, we saw that two of them had been completely cut off.
While occupied in this way the wasp was evidently intensely excited.
She lay on one side with the abdomen bent under, turning the spider
over and over as she worked. After a time she carried it onward to the
potato–field, where the plants afforded some shelter, and placing it
upon a leaf, well above the ground, began to dig near by. She worked
almost entirely with her mandibles, lying sometimes on her side and
sometimes on her back as she cut away the earth, which was pushed
out with the end of her abdomen. When she had worked for ten minutes
and had gone in the length of her body, she picked up the spider and
rapidly made off with it, several times rising on her wings and flying
backward for a few inches. A little further along she again deposited
it on a leaf and began to dig in a fresh place. At the end of twenty
minutes the nest was ready, but in bringing the spider she missed her
direction and carried it to one side. Dropping it on the ground, she
began to hunt about for her hole, but was distracted with excitement
and ran so far afield that we feared she would never find it. At last,
however, she came to the place, ran in for a moment, brought the spider
nearer, dropped it and ran to the nest once more, caught it up again,
and tried to back in with it. She was holding it by the under side of
the body, the venter being toward the hole, and the legs spread out and
stopped its entrance. A moment’s tugging convinced her that this would
not do, and she then turned the spider over, holding it by the back,
whereupon the legs at once folded themselves across the underside of
the thorax, and it was drawn out of sight.
After the egg was laid the wasp came up to the edge of the hole, and
drawing in some earth with her mandibles began to dance up and down
upon it, jamming it into place with her abdomen. Afterwards she came
up higher and drew the dirt in with her first legs, not getting out
of the hole until it was entirely filled up. Then began a remarkable
performance. Bracing herself firmly on her legs she used the end of her
abdomen as an instrument, and with it she now pounded the earth, now
_rubbed_ it, like a pestle in a mortar, and now used it as a brush to
sweep away loose dust. Sometimes she would throw a little earth back
under her body with her mandibles and rub it down with her abdomen.
This part of the work being finished, she spent a few minutes in
sweeping the ground with her first legs, and then brought a quantity
of small objects and placed them over the nest,—a little stick, the
petal of a faded flower, a scrap of dead leaf, and so on, until ten
or twelve things had been collected. This artistic finishing up of
her duties recalled Ammophila; but among our subsequent examples of
fuscipennis we never saw one do her work with such nicety. They were
usually contented to fill in the nest more or less compactly, sometimes
doing much of the work from the outside, to brush off the surface
without any rubbing or pounding, and then to bring two or three little
pebbles or lumps of earth to place over the spot.
So far as we were concerned this was one of the most fearless of the
wasps, not even interrupting her work when we once placed a glass over
her as she was filling her nest; but the approach of an ant would throw
her into a perfect panic, and seizing her spider she would make off
with every sign of terror. It is difficult to understand why wasps of
this species, as well as of biguttatus, never offer combat to the ants
that rob them right and left, but invariably seek safety in retreat.
Their attitude toward other robbers is quite different. We once saw a
fuscipennis that was dragging a Lycosid attacked by a bigger wasp of
the same species. Number One left her spider on the ground and chased
Number Two to a distance; but no sooner had she returned and taken it
up than Number Two, bold and unashamed, was at her heels again, and
the scene was repeated. The object of the robber was to seize a leg
of the spider, and whenever she succeeded in doing this she jerked it
free, and made off with it very rapidly; but when the owner pursued
and caught up with her she relinquished the prize without a struggle.
Why did she? She was the bigger and the stronger, and possession is
nine points of the law in Waspland as elsewhere; but conscience made
a coward of her, while the other was strong in her righteous cause.
After a time we captured the little pirate; but now the nerves of the
rightful owner were completely upset, and she flew away, deserting the
spider for which she had battled so bravely.
The most interesting thing about fuscipennis is her habit of biting the
legs of her victims. The instinct is very irregularly developed, since
four out of ten spiders had not lost any legs, while the others had
been deprived of one or two. No one who has watched the wasp can doubt
that the habit is related to the fact that she makes a very small nest
in comparison to the size of her prey. The spider never went in easily,
always requiring to be shifted and turned and tugged at. There was an
especial tendency to bite at the legs at this point of time, when the
wasp, standing within the tunnel, was trying to drag the spider down.
In one instance she managed to get it past the entrance, but it stuck
in the gallery; and after working at it in that position for a time
she brought it out, subjected the legs to a severe squeezing, and then
tried again. It was still a very bad fit, but by turning it about and
pulling at it she succeeded in getting it in. It may be that the object
of biting the legs is not to remove them, but to render them limber so
that they will bend easily. Whatever the process may be, it is repeated
at intervals from the time the spider is captured. As she carries
it, the wasp pauses again and again, now on bare ground and now in a
sheltered place or on some plant, to renew her efforts at getting the
legs into a satisfactory state.
P. fuscipennis rarely circles about when leaving a place; this is
unfortunate, since her sense of locality seems to be particularly weak.
She nearly always has to hunt for the plant upon which she has placed
her spider, and always loses track of her nest when she tries to bring
the spider to it. We once caught her as she was carrying her spider,
and then released her on the same spot; but she became so much confused
that without our assistance she would never have found it again.
Our acquaintance with Pompilus marginatus began in the middle of July.
She is a small creature, only half an inch long, and is dressed in
black, with a bright orange spot on each side of the anterior part
of the abdomen. We were watching the pretty little Diodonti, as they
filled their holes with aphides, when we saw her going backward,
dragging along a medium–sized spider. Soon she came to an onion flower
that was lying on the ground. Here she stopped and, after a moment’s
hesitation, drew her prey in among the blossoms of the cluster so
that it was hidden from view. It was not long before she came out
and began to fly about near the ground, frequently alighting to poke
her head into cracks and to run again and again into little chance
holes. Never did an insect behave in a more demented manner, and
although there may have been a method in her madness it was difficult
to discover it. No hole nor cranny pleased her, and back she flew to
the onion to see whether her booty were safe. For fifteen minutes she
ran and flew now here, now there, hurry and anxiety in every movement,
returning frequently to reassure herself about the spider. Several
times she entered a hole at the base of a weed, not a made nest, but
an accidental crevice; and this spot was at length chosen either as a
temporary or a final resting place for her spider, since she dragged
it from the onion and deposited it here. We tried to capture the wasp;
but having failed in this, we dug out the spider. It was three inches
down, the hole being deeper than it looked from the outside. There
was no egg upon it. Evidently the work had not been finished, for the
restless creature returned fifteen times within an hour to the broken
nest, either for the purpose of laying her egg or to remove the spider
to another resting–place on her homeward way.
[Illustration: POMPILUS MARGINATUS]
This was our first specimen of marginatus, and a month passed before
we met another. It was while watching some Bembecidæ that we saw the
pretty little orange–spotted worker dragging a small Thomisid across
their nesting–ground. The spider was so small that she held it in her
mandibles well above the ground, and we speak of her as dragging it
only because she walked backward and acted as though she were obliged
to exert herself. Quite often the spiders taken by this species are
too large to be carried, and then it is necessary to drag them; this
habit is so ingrained that when it would be much more convenient to go
straight ahead they stick to the ancient custom, and seem unable to
move in any other way. This little wasp was in a frantic hurry, running
backward into the Bembex holes and then scrambling out again, until
she had crossed the field and had turned to one side, having gone,
since we first saw her, about fifteen feet. Here she dropped the spider
and began to skim over the ground—it could not be called running and
yet it was not flying—until she found a circular hole in the black
earth, which looked as if it ran vertically downward. At the time we
thought that this was a nest that she had made for herself, but we
afterward concluded that it had been excavated by some other creature,
that she had found it and determined to make use of it, and that she
was bringing her prey to the spot with that end in view. Without
entering she rushed back to the spider, but after carrying it a few
inches, dropped it and ran to take another look at the nest. By this
time, however, she was too much excited to know what she was about,
and for five minutes she scurried over the ground without finding it.
During this time she picked up the spider four times, carried it a
little way, and then dropped it. The last time she carried it to the
edge of the grass and stowed it there, this being her first attempt at
concealment. She now found the hole again and brought the spider nearly
to it, but by this time she was perfectly beside herself. The spider
was seized again and again, only to be dropped the next second, while
the wasp rushed back and forth between it and the hole. In time this
method of procedure brought it close to the nest, but it was carried
around the edge once or twice even then. At last, accidentally as it
seemed, it fell in, when the wasp quickly ran in also and pulled it
down. For half an hour she remained inside, and when she came out we
caught her to make sure of her identity. As we set her free immediately
we expected her to go to work at covering her nest, but in this we were
disappointed, for she did not return. We left the place undisturbed
from the thirteenth to the fifteenth of August, when we dug up the
nest. The Thomisid was there, but we could find neither egg nor larva.
The spider was alive, as was shown by a quivering of the legs. This
quivering grew fainter and fainter, until upon the nineteenth it was
scarcely perceptible, and on the twenty–first the spider was dead. Our
first spider had been stung to death at once, while this one lived
seven days and a half after being stored.
On September first, while out in the bean patch, we saw a large Lycosid
running madly, first in one direction and then in another. Hovering
eagerly and excitedly just above was our marginatus, dashing down at
the spider again and again as it came into view for an instant, and
then circling wildly around until it appeared once more. Now she
pounced upon the frightened spider but missed her aim, now she really
grasped it but was shaken off. At last the end came. The wasp descended
upon the doomed spider, and there was a violent struggle, both the
combatants rolling over and over upon the ground, while all that we
could distinguish was the flashing of the red upon the body of the
wasp. In an instant it was over, and the wasp rose, leaving the spider
limp and motionless upon its back. In our other examples of marginatus
the spider taken had been so small that the wasp might easily have
held it and thrust her sting into any spot that she pleased, but this
Lycosid was a different antagonist. Where the two were so nearly
matched, there could have been but slight opportunity for skillful
surgery. In point of strength the wasp was at a disadvantage, and she
must have come off victor by the quick use of her sting. Under these
circumstances she must have struck when and where she could, without
selecting any particular spot. That she quite realized the power of
her foe was shown by her next action. With the utmost circumspection
she settled down upon the spider and made a prolonged and careful
examination of the mouth parts. The investigation was satisfactory,
and without any further stinging she seized the spider by one leg,
and this time really dragged it off. It was a good load for her, and
it evidently required all of her strength to pull it along. Not far
away was a lump of earth, under which the treasure was stowed; and
then began the usual hunting performance, which soon resulted in the
discovery of another cavity which had a very small opening.
She crept in, remained a minute, and then came out and brought her
spider to this new hiding–place. The head went in easily, but it took
a great deal of tugging to get the rest to follow. At last both spider
and wasp were out of sight, and everything remained quiet for so long
that we began to think that this time we were really to see the final
act in the play. But no; when the little wasp came creeping out it was
only to start off on another extended tour, in which we did not attempt
to follow her. She doubtless selected another halting–place, for when
she returned it was to try to get the spider out of the hole by pulling
at one of its hind legs. The task, however, was not an easy one. She
exerted all her strength, so that we expected to see the victim torn to
pieces before our eyes, and still it did not come. At last she seemed
to realize that there was more than one way to accomplish her end, and
turned her attention to cutting away the earth to make the opening
larger. After a few moments’ work she tried again, and although the
passage was still much too small for convenience the spider was at
length dragged forth, looking much the worse for wear. As she moved
away we alarmed her by lifting some vines that prevented our keeping
her in view, and she flew up, leaving the spider on the ground. We
seized the opportunity to bend and twist the plants this way and that
so that the ground might be left uncovered. The changes that we made
probably disconcerted her, for she seemed to lose track of her prey.
For over half an hour she hunted about, circling above the place and
running around and around over the ground. She often came so close to
the spider that we could not understand why she did not see it. At last
it was recovered, and again she started off. We tried to follow her,
but the vines were so thick that, in spite of our efforts, she soon
disappeared into the undiscovered country which we had thus far been
unable to penetrate.
Up to this time we had been entirely unable to understand the actions
of marginatus, and each new example added to our confusion instead of
clearing it away. We were inclined to think that she never made a nest
for herself, but caught her spider and then hurried about for a good
place to store it, and that her absurd conduct was the result of an
indecision of character which made it extremely difficult for her to
choose a place and be contented with it. The last part of this judgment
holds true, even now when we know her whole history, but we have at
last learned that she does dig her own nest.
We had watched a wasp for some time as she carried her spider from
place to place, and finally saw her take it into a crevice among some
rough lumps of earth which she had previously examined. We expected one
of the long spells of eventless waiting to which she had accustomed us,
but on lying down and peering into the hole we found that there was
an opening on the further side, for a ray of light feebly penetrated
the interior. Moving about in this dim illumination was our wasp, and
after a little, we could see, quite distinctly, that she was digging a
hole. This then is her method—to find some sheltered hiding–place where
she may secretly make her nest, that no creature may know where her
treasure is hidden.
We have twice seen a marginatus pick up her spider and fly with it
backward for a long distance—as much as four or five feet. This recalls
the wasp which is said to fly backward before a moving horse and catch
the flies that are hovering over it.
P. marginatus is not troubled by any notion as to the family
connections of the spider that she takes. Anything will do provided she
is strong enough to overcome it and carry it to her nest. The effect of
her sting is quite variable, since in some cases the victim was killed
at once, while in others it was but little affected in the beginning
and lived for eighteen or twenty days.
At eleven o’clock on the morning of a warm day in mid–August we saw the
steel–blue Pompilus scelestus dragging a big Lycosid across a field.
The spider was sixteen millimeters long and wide in proportion, while
the wasp was but thirteen millimeters long and very slender, so that
the weight of the spider was at least three times that of its captor.
The necessity for going backward was evident in this case, but the wasp
moved rapidly considering the load that she was dragging. As she worked
her way along she made frequent pauses, stopping for two or three
minutes at a time in some little hollow, or under leaves or weeds. She
spent a good deal of time, during these pauses, in cleaning herself,
and a good deal of time also in doing something to the spider which we
could not understand. She seemed to be biting the legs, near the body,
beginning with an anterior leg on one side and working backward, and
then repeating the operation on the other side. She went through this
squeezing process again and again, and to us it looked as though she
might be trying to force back the juices from the legs into the body
preparatory to cutting them off; but after a time she would seize her
prey and start on again. She had made her way along in this fashion
for some ten feet, when a second wasp appeared and alighted on a weed
near by. This interloper was a trifle smaller than the other, and from
her actions was evidently greatly interested in the paralyzed spider.
When the Pompilus stopped for a moment the other moved from stem to
stem in a stealthy manner just as a cat stalks a bird. The rightful
owner of the prey was disturbed and dashed at her, driving her away
again and again, but she flew only a short distance and was soon
back, always creeping nearer and nearer to the spider. We, too, were
watching with closest attention, but our desire was to see the speedy
homecoming of Pompilus and to learn whether she cut off the legs of her
victim; and so, interesting as was the contest between the wasp and the
wasp–inquiline, we decided to interfere and remove the intruder. This
was very easily accomplished, since the little insect was so intent
upon following the spider that she was oblivious to our presence, and
allowed us to place a bottle over her as she stood eagerly looking
for a chance to advance. Her removal gave great relief to the other
wasp, as was manifested by an entire change of manner. Before, she
had been constantly on the lookout, moving only with the greatest
circumspection, but now she relaxed her vigilance. With the Ceropales
in our vial we, too, felt relieved, and now the path of discovery
seemed clear before us; but scarcely had things assumed their old
status when a second enemy, a much larger and bolder Ceropales, threw
both the Pompilus and ourselves into consternation. Again we took the
side of our wasp and drove the other one off, but only to see it return
a few moments later. The Pompilus now flew at it in a most gallant
fashion and pursued it far afield, but when she came back the enemy was
but a few seconds behind her. Here we again interposed and removed the
second Ceropales from the field of action.
All cause for anxiety being over, the wasp now resumed her journey.
Before long she came to a shallow depression in the ground which was
partly sheltered by an overhanging lump of earth, and under this
covering she dropped the spider and again began to squeeze its legs.
After a moment she removed it to the other side of the depression,
where it was subjected to further manipulation. Next, her toilet was
attended to, and then the spider was carried back and placed again
under the lump of earth. At least ten times was that limp and helpless
creature dragged from one side to the other of the little depression, a
distance of about two inches, the time between being filled in by the
wasp with cleaning herself and squeezing the legs of her victim. After
forty minutes of this tedious delay the moment came when she picked
up her burden with renewed determination and started rapidly on her
way. We kept very close to her, but she did not allow our presence to
interrupt her work, and, indeed, paid no attention to it. After she had
gone along for a distance of about eight feet there was another pause,
of only five minutes this time, and when she resumed her onward march
it was in a new direction. Thus far she had gone almost due south,
but now she turned and went six feet toward the west. Suddenly the
spider was dropped. There was no hole in sight, but the wasp seemed
to feel that some important crisis had arrived. Her whole manner was
excited and flurried, and we thought that surely we had reached the
neighborhood of the nest. How little we understood her! Her nest was
still far away, and it may be that she had just begun to realize that
the task she had undertaken was too heavy for her accomplishment—that
at her present rate of progress her strength would be exhausted before
she could reach her goal. At any rate, something was wrong. The
spider was left unprotected on the ground while she made a number of
long excursions without it, sometimes being gone as much as fifteen
minutes. On coming back from these trips she would return to the task
of squeezing the legs with such energy and persistence that we expected
to see them drop off. Then she would run over the ground in all
directions, looking under lumps of earth and stones and poking her head
into every little hole. Was she trying to find some suitable spot near
at hand to take the place of the one which she had prepared or selected
at a distance?
One hour from the time of her arrival at this place, and two hours from
the time that we began to watch her, she flew away and was gone for an
unusually long time. We can only suppose that when she absented herself
in this way she was visiting the spot to which she wished to convey her
booty. On her return she seemed to be filled with a new idea, for after
climbing to the top of a tall stout weed that grew near by, she came
down, seized the spider, and tried to drag it up the stem. Perhaps she
meant to lift it to such an elevation that she could fly with it, but
it was too heavy for her and fell after she had raised it to a height
of three inches. She then flew away again, and on her return we caught
her, fearing that she was becoming discouraged and that she might
presently depart to be seen no more. Had there been any prospect of her
solving the difficulty that beset her our patience might have held out
to the end, but this was evidently a case in which there was a failure
of instinct, or intelligence, or whatever faculty was concerned.
More than a year passed before we had another opportunity of solving
this problem of scelestus, and the pleasure with which we hailed her
second appearance in our garden may be easily imagined. This time the
wasp had made her nest, but was not ready to fill it, and when we first
saw her she was running about without any particular aim in view,
although at the time we supposed her to be hunting. Before long she
went and took a look at the neat round hole which she had made near the
fence that separates the garden from the woods. The earth that had been
taken out either had been carried to a distance or had been swept away
after the digging was completed, for there was no pile to be seen. This
was at two o’clock of a cloudy afternoon. It may be that she needed the
stimulus of sunshine to make her hunt, or perhaps she realized that
what was left of the day would not give her sufficient time to capture
her spider and bring it home. At any rate, she spent the remainder of
the afternoon in making short excursions around her nest, attended, at
a little distance, by a smaller blue wasp, Pompilus subviolaceus, whose
presence she did not seem to notice. These trips took her from ten to
twenty feet from the nest, each occupying from fifteen minutes to half
an hour. At every return to the nest she flattened herself out on the
ground and wriggled in the dust, and then dragged herself all around
it in the strangest manner. Perhaps these actions were indications of
pleasurable emotion. We had seen them once before, in Priononyx atrata
just before she carried a locust into her nest.
At a little after four o’clock she began to investigate, very
carefully, the plants and grasses that immediately surrounded her hole,
showing an especial interest in one bunch of clover that grew four
inches away. Into this she finally vanished, and peering curiously
among the greenery, we discovered her hanging to a leaf, which was
sheltered by thick foliage on all sides. Here she remained motionless
and probably fast asleep until sundown, when we left her for the night.
When we went to the garden at eight o’clock on the following morning,
subviolaceus was on hand, but scelestus was still sound asleep in her
leafy bower. We thought it best to awaken her, for a large spider
had spread its web just below, and if the wasp should drop upon it
nothing could save her. We therefore aroused her gently, whereupon she
crept slowly up the stem and, taking her stand on the highest point,
surveyed the world. Then, after stretching herself sleepily, she made
her toilet, cleaning off her wings and legs, and washing her face with
her feet like a cat. When these duties were finished she walked slowly
about for an hour, visiting her nest every now and then. Suddenly, at
half past nine o’clock, her whole manner changed, and seeming very much
excited she ran rapidly along, parallel with the fence, for fifteen
or twenty feet, and then, rising on her wings, flew far away into the
woods. She had evidently gone hunting at last, and we watched eagerly
for her return. She was not successful at once, however, for at half
past ten she came back without anything, stayed at the nest for a
few minutes, and then flew to the woods again with the same excited
manner as before. Perhaps she had already caught her spider at some far
distant spot, and was getting her bearings preparatory to bringing it
home; but it was half past one when she suddenly appeared, five or six
inches from the nest, coming backward through the fence, and dragging a
large Lycosid. This she laid down close by, and began to bite at the
legs quite after the manner of the wasp we had seen the year before.
Her movements were full of nervous excitement, in marked contrast to
those of the previous day. Presently she went to look at her nest, and
seemed to be struck with a thought that had already occurred to us—that
it was decidedly too small to hold the spider. Back she went for
another survey of her bulky victim, measured it with her eye, without
touching it, drew her conclusions, and at once returned to the nest
and began to make it larger. We have several times seen wasps enlarge
their holes when a trial had demonstrated that the spider would not go
in, but this seemed a remarkably intelligent use of the comparative
faculty. Her method of work was peculiar. Standing in the tunnel with
her head down and her abdomen curved under, she bit the earth loose
with her mandibles and pushed it under her body and beyond the tip of
the abdomen. When a little had accumulated she backed out, holding it
in this way.
While she was thus employed the spider was attacked by a very tiny
red ant, that could not by any possibility have stirred it. When the
wasp caught sight of this insignificant marauder she fell into a fit
of wild fury, and bending her abdomen under, seized the ant again and
again in her mandibles, and flung it backward against the tip of her
sting. The little creature finally escaped, seeming none the worse for
the rough handling to which it had been subjected, while the wasp,
still trembling with excitement, grasped her spider and rushed off to
a distance of several feet, carrying it up on a weed and depositing
it there. The labor of excavation was then resumed, and after a
half–hour’s work the nest was completed to her satisfaction.
Coming up head first, she flattened herself out on the ground, and
sprawling thus, dragged herself all around it. The spider was now
brought to the nest, being left once on the way while she ran in and
out again, and was taken in after a new and original fashion. Backing
in herself, she seized it by the tip of the abdomen and dragged it down
without any trouble, since the legs were gently pushed up over the head
and made no resistance.
In two minutes she emerged from the opening, and standing on the four
posterior legs, with her abdomen hanging down into the hole, scratched
the earth backward with the front legs and mandibles. As it fell in
she pushed it down with the abdomen, and as the hole filled she raised
herself higher and higher on her legs, still using the tip of the
abdomen to work the material into place.
When the filling of the nest was nearly completed, we caught the
wasp, and after taking the spider, threw back the earth into the
hole. Subviolaceus, who had watched the homecoming from a respectful
distance, now felt that her turn had come, and descending upon the spot
began to dig. Not finding anything, she shifted her position several
times, and worked industriously, even returning after we had frightened
her away. Sharp says that a Ceropales has been observed to oviposit
on a spider, not while it was being carried in, but subsequently by
entering the nest for the purpose; and the actions of subviolaceus
pointed to similar intentions on her part. We have watched her for
an hour at a time running into the open nests on the Bembex field,
sometimes coming out again directly and sometimes remaining inside
for several minutes. It is not likely that she would utilize the
flies of Bembex, but it may be that she was looking for the Pompelid
nests that are often made in the same locality. Scelestus did not
notice subviolaceus, and it is difficult to see why a wasp should be
disturbed by the presence of a parasite. In making and storing her
nest she is the blind instrument of an impelling power; she knows
what she must do, but not why she does it. Her descendants are in
most cases as completely outside of her experience as her ancestors,
and how should she guess that the presence of a certain fly or wasp
means danger to her race? Of what happens to her egg after she leaves
it she is so absolutely ignorant that she might easily look on with
serene indifference at the destruction of her own larva by that of the
intruder. In Astata we see, as might be expected, a calm tolerance of
the visits of the Chrysis fly, but the uneasiness of scelestus herself
at the sight of Ceropales and the valorous defense of Trypoxylon
show more highly developed instincts. Bembex, too, deeply resents
the presence of parasites, although after the deed is done she feeds
their young without questioning their right to her care. Among bees,
Andrena, and Nomada, which is parasitic upon it, are said to live on
most friendly terms; but in other genera there is a deep–seated enmity
between host and parasite.
[Illustration: THE HOME–COMING OF SCELESTUS]
In the literature of the Hymenoptera references have been made from
time to time to certain wasps that cut off the legs of spiders or other
creatures before storing them away; but observations on the subject
have been rare and not very definite. Brehm, in the “Thierleben,”
says that Agenia punctata builds nests of mud, and places in each
cell one moderately large spider from which she has first removed all
the legs. The most interesting notes on the subject have been made
by M. Goureau, who gives an account of finding two spiders that had
been mutilated by wasps, one of them having had all of the legs cut
off, and the other all but the first pair. At another time a wasp that
was flying near him let fall a spider, which he captured before it
could be recovered by the owner. The wasp escaped, so that he could
not determine the species, but the spider’s legs had been removed. He
concluded that instead of stinging the spiders the wasps had mutilated
them so that they could not run away. He does not seem to realize that
death would certainly result from such an operation.
[Illustration: NEST OF AGENIA BOMBYCINA]
Vespa germanica often cuts off the wings of a dead wasp, or even cuts
its body into two parts, before flying away with it, but this is only
when the captured insect is too large to be handled in any other way;
and Pompilus fuscipennis sometimes cuts off one or more legs from her
spider, although without any regular method of procedure.
Agenia bombycina finds a nesting–place to her liking on our
smoke–house, in the crevice between the bricks and the wooden
door–frame, where she makes clusters of little mud cells, putting one
mutilated spider into each, and storing about one a day. Her locality
sense is unusually poor, owing apparently to her intense nervousness
and excitability, but some individuals are better endowed than others
in this respect.
[Illustration: LYCOSA KOCHII, FOUND IN NEST OF AGENIA BOMBYCINA]
On a bright morning in the middle of August we stationed ourselves by
the smoke–house at eight o’clock, and half an hour later an Agenia
began to bring lumps of earth, working out of sight under the door
frame. She kept at it steadily, spending three or four minutes in
getting a load and one or two in placing it. At twelve o’clock, her
nest being ready, she flew away to hunt for a spider. So long as a wasp
comes and goes at frequent intervals time slips away rapidly, but to
keep one’s attention unflagging through hours of watching is weariness
to the flesh. We saw no more of our Agenia until three, when she
appeared, half walking, half flying through the grass, going forward.
Her spider was held by the spinnerets, and being larger than she was it
trailed behind her. On reaching the wall she began to climb; but the
weight of the spider made her fall again and again, and forty minutes
passed in wearisome toil before it was safely put away. The egg having
been laid, she began to bring earth for closing, and we felt thankful
that our task as well as hers was nearly over. She worked slowly
now, taking ten or fifteen minutes for a trip; but after bringing in
the sixth pellet she took on a livelier air, and before long we were
convinced that she had begun to build a new cell. For two hours longer
we watched her unremitting labor, and when we left her at six o’clock
she was flying back and forth as briskly as ever.
Another Agenia, less ambitious, brought her spider at three o’clock
and then went to bed in an empty cell, head in, tail sticking out. We
cut away a section of the door–frame that covered the spot without
disturbing her slumber. This one could never remember where her nest
was, but had a long hunt for it every time she brought a pellet; and
when she had caught the spider she lost herself completely on the brick
wall, going to the very top, and even around the corner on to the side
of the building. Every little while she would fly back to the grass at
the threshold and start up afresh, and in this way she finally stumbled
on the right spot by accident. This seemed very stupid of her, as she
made many locality studies. Her behavior was in striking contrast to
little Rhopalum’s unerring choice of one tiny pin–hole among hundreds
just like it.
The larva of bombycina cocoons nine days after the egg is laid. The
spiders that we found in the cells were dead even when taken on the
day of storing. There was no rule about the degree of mutilation, one
having seven legs left, two five, one two, and four none. We have no
doubt that the object of this curious habit is to save room in the
nest.